1. Field of the Invention
The present invention relates generally to a tool or an article that carries a coating that is applied according to a PVD or a CVD method. The invention preferably relates to a tool for the cutting of metals, in particular austenitic steels, nickel-based alloys and titanium as well as titanium alloys.
2. Discussion of Background Information
Precipitation hardenable iron-cobalt-molybdenum and/or tungsten alloys are known as tool materials. The production of large tools from these so-called high-speed cutting alloys, however, is associated with a number of problems because, on the one hand, there is a high segregation tendency during the solidification of the melt and, on the other hand, a hot working of the material is possible only within narrow limits at high temperatures.
It has already been proposed (WO 01/91962) to form the tool as a composite tool, only small cutting parts of which are made of an iron-cobalt-tungsten alloy, which parts are connected by welding to a carrier part, usually made of an alloyed steel. It is expected that an improvement of the performance of the cutting parts will be achieved through a powder-metallurgical (PM) production.
In order to increase the edge-holding ability of tools, it has been customary to provide at least the working areas of the cutting tools with a hard surface coating. After the production of the tool in its shape and a heat treatment of the same, at least one layer of hard material, usually of carbide and/or nitride as well as carbon nitride and/or oxide, in particular of the elements Ti and/or Al and/or Cr, is applied according to the PVD or CVD process at temperatures between 500° and 680° C., at the most below the tempering temperature of the tool steel alloy, in particular the high-speed steel alloy.
A hard material coating is also known for hard metals and is widely applied for such tools.
In the past the precipitation-hardened Fe—Co—Mo/W alloys mentioned at the outset as cutting part materials produced improved durability of the tools, particularly when Ti-based materials and the like materials were processed. However, the technological further development of coated high-speed steel tools improved their quality and performance such that tools of carbon-free precipitation-hardened (Fe—Co—Mo) cutting parts with the same coating also have approximately the same property profile or the same edge-holding ability in cutting.
It would be advantageous to have available a tool or an article with much improved performance, particularly in the cutting of metals such as titanium.